Just as a postscript to the Martha Coakley lawsuit (which I’ll have more on in a bit), it was supposed to be her failure to beat Scott Brown that ruined the Democratic Party for generations. As it turned out, she’s doing her job as a public servant, and Brown could have a short-lived Senate career, with a very attractive replacement. Elizabeth Warren has taken the lead in the closely watched US Senate race, according to a new poll out of UMass-Amherst.

Warren leads Brown by 4 points among registered voters in the UMass Amherst Poll, 43 percent to 39 percent, the difference being within the 4.4 percent margin of error, say UMass Amherst political scientists Brian Schaffner and Ray La Raja. The poll finds Warren is drawing strong support from women, middle-to-low income residents and younger voters. Brown maintains a large lead among Independent voters while Warren is getting overwhelming support from Democratic voters in Massachusetts.

“These numbers could mean trouble for Scott Brown,” Schaffner says. “The race is a dead heat and his support is well under 50 percent, which usually means difficulty for an incumbent, especially this far out from Election Day.”

In fact, his support in this poll is under 40%, which is nearly fatal. Warren will also have the benefit of a Presidential election year, which will boost turnout.

Warren’s success and the enthusiasm around her campaign has knocked every potential challenger in the Democratic primary out of the race. She has the ability to stay competitive with the Wall Street-backed Brown in fundraising, and the attacks put forward by the likes of Karl Rove have been laughable. Warren is still a neophyte candidate and a lot can go wrong; she probably needs to improve among independents, and you could see some gaffes and distortions of her record coming into play. But at the moment, she is well-positioned to enter the Senate.

At this point, come 2013 I’d rather have Martha Coakley and Elizabeth Warren taking it to the banking industry than Coakley in the Senate and someone who may not have the same perspective on foreclosure fraud in the Attorney General’s chair.